1. Field of the Invention
This invention relates generally to a coating machine for a silk screen printing operation and more particularly to a machine for coating both a liquid emulsion as well-as capillary film to a screen wherein the scoop or applicator is held relatively stationary and the screen is moved during the application process.
2. Description of the Prior Art
A screen which is used in the silk screen industry has typically from fifty threads to up to four or five hundred threads per inch. This screen then becomes a type of printing plate. Either a liquid or dry emulsion may be applied to the screen. When a liquid emulsion is applied to the screen, this typically is a manual operation and is completed by holding the screen at an angle away from the worker and running a scoop or coater, containing the liquid emulsion, on the screen. This process is quite typically repeated on both sides of the screen. The goal is to obtain a very consistent and smooth coating so that a consistent smooth print image is obtained.
While this appears to be a relatively simple manual operation, there are several drawbacks with this method. After repeated motion, the operators arm becomes fatigued and subject to muscle stress. There is a definite skill in applying the right pressure as well as moving the coater at the correct speed in order to obtain the proper coating thickness. When applying the coating, the operator is moving the coater away from himself and therefore is not in a good position to see the coating which is being applied. Without being able to see the coating, it is difficult to control the coating speed.
Sophisticated mechanized and computer controlled machines are available, such as the H41E from Harlicher Ag in Germany. The machine places the screen in a fixed position and the coating troughs containing the emulsion are moved up the screen on one or both sides. This is typically a very sophisticated piece of equipment, requires much time to set up and is not always economical to purchase when one is producing small lot sizes of screens.
When a dry emulsion, typically applied as a capillary film, is coated on a screen, this can also be done either manually or by means of a sophisticated mechanized computer controlled machine. When done manually, the screen is thoroughly wetted and the capillary film is placed on top of the screen, which is either vertical or at an angle away from the worker. The film and screen are at such an angle that the water, by the force of gravity, tends to be driven away from the film. After the film is applied, the operator may or may not squeegy away excess water. This squeegy action may deform the film.
The present invention addresses the problems associated with the prior and provides both a method and apparatus for applying a liquid emulsion as well as a method and apparatus for applying a dry emulsion. In addition, the invention addresses the problem of having the ability to do both processes without the use of extensive set up time and provides for a universal coating machine for use in applying either a liquid emulsion or a dry emulsion to a screen.